stdint.h

, stdint

- integer types

Synopsis

#include <stdint.h>

Description

The <stdint.h> header declares sets of integer types having specified widths, and
defines corresponding sets of macros. It also defines macros that specify limits
of integer types corresponding to types defined in other standard headers.

The ``width'' of an integer type is the number of bits used
to store its value in a pure binary system; the actual type
can use more bits than that (for example, a 28-bit type could
be stored in 32 bits of actual storage). An N-bit signed type
has values in the range -2N-1 or 1-2N-1 to 2N-1-1, while an N-bit
unsigned type has values in the range 0 to 2N-1.

For each type described herein that the implementation provides, the <stdint.h> header
declares that typedef name and defines the associated macros. Conversely, for each
type described herein that the implementation does not provide, the <stdint.h> header
does not declare that typedef name, nor does it define the associated
macros. An implementation provides those types described as required, but need not
provide any of the others (described as optional).

Integer Types

When typedef names differing only in the absence or presence of the
initial u are defined, they denote corresponding signed and unsigned types as
described in the ISO/IEC 9899: 1999 standard, Section 6.2.5; an implementation providing
one of these corresponding types must also provide the other.

In the following descriptions, the symbol N represents an unsigned decimal integer
with no leading zeros (for example, 8 or 24, but not 04
or 048).

Exact-width integer types

The typedef name intN_t designates a signed integer type with width N, no padding bits, and a two's-complement representation. Thus, int8_t denotes a signed integer type with a width of exactly 8 bits.

The typedef name uintN_t designates an unsigned integer type with width N. Thus, uint24_t denotes an unsigned integer type with a width of exactly 24 bits.

The following types are required:

int8_t
int16_t
int32_t
uint8_t
uint16_t
uint32_t

If an implementation provides integer types with width 64 that meet these requirements, then the following types are required:

int64_t
uint64_t

In particular, this is the case if any of the following are true:

The implementation supports the _POSIX_V6_ILP32_OFFBIG programming environment and the application is being built in the _POSI X_V6_ILP32_OFFBIG programming environment (see the Shell and Utilities volume of IEEE Std 1003.1-200x, c99, Programming Environments).

The implementation supports the _POSIX_V6_LP64_OFF64 programming environment and the application is being built in the _POSIX_ V6_LP64_OFF64 programming environment.

The implementation supports the _POSIX_V6_LPBIG_OFFBIG programming environment and the application is being built in the _POSIX_V6_LPBIG_OFFBIG programming environment.

All other types of this form are optional.

Minimum-width integer types

The typedef name int_leastN_t designates a signed integer type with a width of at least N, such that no signed integer type with lesser size has at least the specified width. Thus, int_least32 _t denotes a signed integer type with a width of at least 32 bits.

The typedef name uint_leastN_t designates an unsigned integer type with a width of at least N, such that no unsigned integer type with lesser size has at least the specified width. Thus, uint_ least16_t denotes an unsigned integer type with a width of at least 16 bits.

Each of the following types designates an integer type that is usually fastest to operate with among all integer types that have at least the specified width.

The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear grounds for choosing one type over another, it will simply pick some integer type satisfying the signedness and width requirements.

The typedef name int_fastN_t designates the fastest signed integer type with a width of at least N. The typedef name uint_fastN_ t designates the fastest unsigned integer type with a width of at least N.

Designates a signed integer type with the property that any valid pointer to void can be converted to this type, then converted back to a pointer to void, and the result will compare equal to the original pointer.

uintptr_t

Designates an unsigned integer type with the property that any valid pointer to void can be converted to this type, then converted back to a pointer to void, and the result will compare equal to the original pointer.

On standard-conforming systems, the intptr_t and uintptr_t types are required; otherwise, they are optional.

Greatest-width integer types

intmax_t

Designates a signed integer type capable of representing any value of any signed integer type.

uintmax_t

Designates an unsigned integer type capable of representing any value of any unsigned integer type.

These types are required.

Applications can test for optional types by using the corresponding limit macro from Limits of Specified-Width Integer Types.

Limits of Specified-Width Integer Types

The following macros specify the minimum and maximum limits of the types
declared in the <stdint.h> header. Each macro name corresponds to a similar
type name in Integer Types.

Each instance of any defined macro is replaced by a constant expression
suitable for use in #if preprocessing directives. This expression has the same
type as would an expression that is an object of the corresponding
type converted according to the integer promotions. Its implementation-defined value is equal to
or greater in magnitude (absolute value) than the corresponding value given
below, with the same sign, except where stated to be exactly the
given value.

Limits of exact-width integer types

Minimum values of exact-width signed integer types:

{INTN_MIN}

Exactly -(2N-1)

Maximum values of exact-width signed integer types:

{INTN_MAX}

Exactly 2N-1 -1

Maximum values of exact-width unsigned integer types:

{UINTN_MAX}

Exactly 2N -1

Limits of minimum-width integer types

Minimum values of minimum-width signed integer types:

{INT_LEASTN_MIN}

-(2N-1 -1)

Maximum values of minimum-width signed integer types:

{INT_LEASTN_MAX}

2N-1 -1

Maximum values of minimum-width unsigned integer types:

{UINT_LEASTN_MAX}

2N -1

Limits of fastest minimum-width integer types

Minimum values of fastest minimum-width signed integer types:

{INT_FASTN_MIN}

-(2N-1 -1)

Maximum values of fastest minimum-width signed integer types:

{INT_FASTN_MAX}

2N-1 -1

Maximum values of fastest minimum-width unsigned integer types:

{UINT_FASTN_MAX}

2N-1 -1

Limits of integer types capable of holding object pointers

Minimum value of pointer-holding signed integer type:

{INTPTR_MIN}

-(215 -1)

Maximum value of pointer-holding signed integer type:

{INTPTR_MAX}

215 -1

Minimum value of pointer-holding signed integer type:

{UINTPTR_MAX}

216 -1

Limits of greatest-width integer types

Minimum value of greatest-width signed integer type:

{INTMAX_MIN}

-(263 -1)

Maximum value of greatest-width signed integer type:

{INTMAX_MIN}

263 -1

Maximum value of greatest-width unsigned integer type:

{UINTMAX_MIN}

264 -1

Limits of Other Integer Types

The following macros specify the minimum and maximum limits of integer types
corresponding to types defined in other standard headers.

Each instance of these macros is replaced by a constant expression suitable
for use in #if preprocessing directives. This expression has the same type
as would an expression that is an object of the corresponding type
converted according to the integer promotions. Its implementation-defined value is equal to or
greater in magnitude (absolute value) than the corresponding value given below, with
the same sign.

Limits of ptrdiff_t:

{PTRDIFF_MIN}

-65535

{PTRDIFF_MAX}

+65535

Limits of sig_atomic_t:

{SIG_ATOMIC_MIN}

See below.

{SIG_ATOMIC_MAX}

See below.

Limits of size_t:

{SIZE_MAX}

65535

Limits of wchar_t:

{WCHAR_MIN}

See below.

{WCHAR_MAX}

See below.

Limits of wint_t:

{WINT_MIN}

See below.

{WINT_MAX}

See below.

If sig_atomic_t (see the <signal.h> header) is defined as a signed integer
type, the value of {SIG_ATOMIC_MIN} is no greater than -127 and the
value of {SIG_ATOMIC_MAX} is no less than 127. Otherwise, sig_atomic_t is defined
as an unsigned integer type, the value of {SIG_ATOMIC_MIN} is 0, and
the value of {SIG_ATOMIC_MAX} is no less than 255.

If wchar_t (see the <stddef.h> header) is defined as a signed integer
type, the value of {WCHAR_MIN} is no greater than -127 and
the value of {WCHAR_MAX} is no less than 127. Otherwise, wchar_t is defined
as an unsigned integer type, and the value of {WCHAR_MIN} is 0
and the value of {WCHAR_MAX} is no less than 255.

If wint_t (see the <wchar.h> header) is defined as a signed integer
type, the value of {WINT_MIN} is no greater than -32767 and the
value of {WINT_MAX} is no less than 32767. Otherwise, wint_t is defined as
an unsigned integer type, and the value of {WINT_MIN} is 0 and
the value of {WINT_MAX} is no less than 65535.

Macros for Integer Constant Expressions

The following macros expand to integer constant expressions suitable for initializing objects
that have integer types corresponding to types defined in the <stdint.h> header.
Each macro name corresponds to a similar type name listed under minimum-width
integer types and greatest-width integer types.

Each invocation of one of these macros expands to an integer constant
expression suitable for use in #if preprocessing directives. The type of the
expression has the same type as would an expression that is an
object of the corresponding type converted according to the integer promotions. The value
of the expression is that of the argument. The argument in any
instance of these macros is a decimal, octal, or hexadecimal constant with
a value that does not exceed the limits for the corresponding type.

Macros for minimum-width integer constant expressions

The macro INTN_C(value) expands to an integer constant expression corresponding to the type int_leastN_t. The macro UINTN_C(value) expands to an integer constant expression corresponding to the type uint_leastN_t. For example, if uint_least64_t is a name for the type unsigned long long, then UINT64_C(0x123) might expand to the integer constant 0x123ULL.

Macros for greatest-width integer constant expressions

The following macro expands to an integer constant expression having the value specified by its argument and the type intmax_t:

INTMAX_C(value)

The following macro expands to an integer constant expression having the value specified by its argument and the type uintmax_t: